The spine is comprised of twenty-four vertebrae that are stacked one upon the other to form the spinal column. The spine provides strength and support to allow the body to stand and to provide flexibility and motion. Each vertebra includes an opening through which the spinal cord passes enabling the spine to protect the spinal cord.
Between each pair of vertebrae is an intervertebral disc. The disc is composed of three component structures: (1) the nucleus pulposus; (2) the annulus fibrosus; and (3) the vertebral endplates. The disc serves several purposes, including absorbing shock, relieving friction, and handling pressure exerted between the superior and inferior vertebral bodies associated with the disc. The disc also absorbs stress between the vertebral bodies, which stress would otherwise lead to degeneration or fracture of the vertebral bodies.
Disorders of the spine are some of the costliest and most debilitating health problems facing the populations of the United States and the rest of the world, costing billions of dollars each year. Moreover, as populations of developed countries continue to age, the incidence of spinal disorders will continue to grow. Typical disorders include those caused by degeneration, trauma, genetic disorders, or other causes.